Sisymbrium sylvestre Linnaeus, Sp. Pl. 2: 657. 1753; Brachiolobos sylvestris (Linnaeus) Allioni; Nasturtium sylvestre (Linnaeus) W. T. Aiton; Radicula sylvestris (Linnaeus) Druce

Perennials; glabrous or sparsely pubescent. Stems prostrate, decumbent, ascending, or suberect, branched mainly basally, (0.5-)1.5-8(-10) dm. Basal leaves not rosulate; similar to cauline. Cauline leaves petiolate, or (distal) often subsessile; blade deeply pinnatisect, (lobes 3-6 on each side, sublinear, lanceolate, oblong, elliptic, or ovate), (2-)3.5-15(-20) cm × (7-)10-45(-60) mm, base usually not auriculate, rarely minutely auriculate, margins dentate, serrate, subentire, or (distally) pinnatisect, (lobes 1-3 on each side). Racemes elongated. Fruiting pedicels divaricate, straight, (3-)4-10(-12) mm. Flowers: sepals ascending or spreading, oblong, 1.8-3(-3.5) × 0.7-1.5 mm; petals yellow, spatulate or obovate, (2.2-)2.8-5.5(-6) × 1.5-2.5 mm; median filaments (1.5-)1.8-3.5(-4) mm; anthers oblong, 0.7-1 mm. Fruits siliques, straight, usually linear, rarely oblong-linear, 10-20(-25) × (0.7-) 1-1.3(-1.6) mm; valves glabrous; ovules 24-80 per ovary; style 0.5-1(-1.5) mm. Seeds (rarely produced), usually uniseriate, rarely sub-biseriate, reddish brown, ovoid, 0.5-0.9 mm (0.4-0.5 mm diam.), colliculate. 2n = 32, 40, 48.

Flowering May-Aug. Along ditches, damp areas, shores of ponds and lakes, sandy beaches, waste grounds, ditches, wet roadsides, meadows, washes, fields, gardens; 0-2500 m; introduced; Alta., B.C., N.B., Nfld. and Labr. (Nfld.), Ont., P.E.I., Que.; Ala., Ark., Colo., Conn., Del., D.C., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., R.I., Tenn., Utah, Vt., Va., Wash., W.Va., Wis.; Europe; sw Asia; introduced also in South America.